Method for forming a flat bottom electrode via (BEVA) top surface for memory

ABSTRACT

Various embodiments of the present application are directed towards a method for forming a flat via top surface for memory, as well as an integrated circuit (IC) resulting from the method. In some embodiments, an etch is performed into a dielectric layer to form an opening. A liner layer is formed covering the dielectric layer and lining the opening. A lower body layer is formed covering the dielectric layer and filling a remainder of the opening over the liner layer. A top surface of the lower body layer and a top surface of the liner layer are recessed to below a top surface of the dielectric layer to partially clear the opening. A homogeneous upper body layer is formed covering the dielectric layer and partially filling the opening. A planarization is performed into the homogeneous upper body layer until the dielectric layer is reached.

REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/547,230, filed on Aug. 18, 2017, the contents of which areincorporated herein by reference in their entirety.

BACKGROUND

Many modern day electronic devices include non-volatile memory.Non-volatile memory is electronic memory that is able to store data inthe absence of power. Some promising candidates for the next generationof non-volatile memory include resistive random-access memory (RRAM) andmagnetoresistive random-access memory (MRAM). RRAM and MRAM haverelatively simple structures, and are compatible with complementarymetal-oxide-semiconductor (CMOS) logic fabrication processes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of anintegrated circuit (IC) comprising a memory cell on a flat bottomelectrode via (BEVA) top surface.

FIG. 2 illustrates a cross-sectional view of some more detailedembodiments of the IC of FIG. 1.

FIG. 3 illustrates a cross-sectional view of some more detailedembodiments of the IC of FIG. 2.

FIGS. 4-6, 7A-7C, 8-20 illustrate a series of cross-sectional views ofsome embodiments of a method for forming an IC comprising a memory cellon a flat BEVA top surface.

FIG. 21 illustrates a flowchart of some embodiments of the method ofFIGS. 4-6, 7A-7C, 8-20.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

According to a method for forming an integrated circuit (IC), a bottomelectrode via (BEVA) dielectric layer is formed covering a metal wire ofa back-end-of-line (BEOL) interconnect structure. An etch is performedinto the BEVA dielectric layer to form a BEVA opening exposing the metalwire. A metal blocking layer is formed covering the BEVA dielectriclayer and conformally lining the BEVA opening, such that the metalblocking layer partially fills the BEVA opening. A metal layer is formedcovering the metal blocking layer and filling a remainder of the BEVAopening over the metal blocking layer. A planarization is performed intothe metal layer and the metal blocking layer until the BEVA dielectriclayer is reached, thereby forming a BEVA in the BEVA opening. The BEVAcomprises a BEVA body formed from the metal layer, and further comprisesa BEVA liner lining the BEVA body and formed from the metal blockinglayer. A memory cell is then formed directly on a top surface of theBEVA.

A challenge with the method is that the metal layer and the metalblocking layer have different hardness values, such that theplanarization removes the metal layer and the metal blocking layer atdifferent rates. Accordingly, the top surface of the BEVA is uneven orrough. For example, a top surface of the BEVA body may be verticallyoffset from a top surface of the BEVA liner.

Because the top surface of the BEVA is uneven or rough, the electricfield across the memory cell is non-uniform. The non-uniform electricfield may, in turn, lead to poor yield and/or non-uniform performanceduring bulk manufacture of the IC. As feature sizes continue to shrinkin ICs, BEVAs and memory cells will also shrink, such that electricfield uniformity will be increasingly important in memory cells.

In view of the foregoing, various embodiments of the present applicationare directed towards a method for forming a flat BEVA top surface formemory, as well as an IC resulting from the method. In some embodiments,an etch is performed into a via dielectric layer to form an openingoverlying and exposing a conductive wire underlying the via dielectriclayer. A via liner layer is formed covering the via dielectric layer andlining the opening. The via liner layer partially fills the opening. Alower via body layer is formed covering the via dielectric layer andfilling a remainder of the opening over the via liner layer. A topsurface of the lower via body layer and a top surface of the via linerlayer are recessed to below a top surface of the via dielectric layer topartially clear the opening, and to form a via liner and a lower viabody in the opening. An upper via body layer is formed covering the viadielectric layer, and filling a portion of the opening cleared by therecessing. The upper via body layer is homogeneous. A planarization isperformed into the upper via body layer until the via dielectric layeris reached to form an upper via body in the opening, and overlying thelower via body and the via liner. Collectively, the upper via body, thelower via body, and the via liner define a via in the opening.

Because the upper via body layer is homogeneous, the upper via bodylayer has a substantially uniform hardness and the planarization removesthe upper via body layer at a substantially uniform rate. This, in turn,forms the upper via body with a top surface that is homogeneous, andthat is flat or substantially flat. Further, because the top surfacesrespectively of the lower via body and the via liner are recessed in theopening, the top surface of the upper via body completely defines a topsurface of the via. As such, the top surface of the via is homogeneous,and is flat or substantially flat. Because the top surface of the via isflat or substantially flat, the electric field produced across a memorycell directly on the upper via body may be uniform or substantiallyuniform.

With reference to FIG. 1, a cross-sectional view 100 of some embodimentsof an IC comprising a memory cell 102 is provided. As illustrated, thememory cell 102 is on a lower dielectric layer (e.g., via dielectriclayer) 104 and a BEVA (e.g., via) 106. The memory cell 102 reversiblychange between a first data state and a second data state depending upona voltage applied across the memory cell 102. In some embodiments, thememory cell 102 is a resistive random-access memory (RRAM) cell, amagnetoresistive random-access memory (MRAM) cell, or some othersuitable type of memory cell. Further, in some embodiments, the memorycell 102 comprises a bottom electrode 108, a data storage element 110,and a top electrode 112.

The bottom electrode 108 overlies the lower dielectric layer 104 and theBEVA 106. In some embodiments, the bottom electrode 108 directlycontacts a top surface 106 t of the BEVA 106, and/or directly contacts atop surface 104 t of the lower dielectric layer 104. The bottomelectrode 108 may be or comprise, for example, tantalum nitride,titanium nitride, platinum, iridium, ruthenium, tungsten, silver,copper, some other suitable conductive material(s), or any combinationof the foregoing. As used herein, a term (e.g., conductive material)with a suffix of “(s)” may, for example, be singular or plural.

The data storage element 110 overlies the bottom electrode 108, and thetop electrode overlies the data storage element 110. The data storageelement 110 reversibly changes between a first data state and a seconddata state depending upon a voltage applied across the memory cell 102.In some embodiments where the memory cell 102 is a RRAM cell, the datastorage element 110 is or comprises hafnium oxide, some other suitablehigh κ dielectric(s), some other suitable dielectric(s), or anycombination of the foregoing. As used herein, a high κ dielectric is adielectric with a dielectric constant κ greater than about 3.9, 5, 10,15, or 20. In some embodiments where the memory cell 102 is a MRAM cell,the data storage element 110 is or comprises a magnetic tunnel junction(MTJ) or some other suitable magnetic data storage structure. The topelectrode 112 may be or comprise, for example, titanium nitride,tantalum nitride, platinum, iridium, tungsten, some other suitableconductive material(s), or any combination of the foregoing.

The lower dielectric layer 104 separates the memory cell 102 from alower wire (e.g., conductive wire) 114 underlying the memory cell 102and the BEVA 106. The lower dielectric layer 104 may be or comprise, forexample, silicon dioxide, silicon oxynitride, a low κ dielectric,silicon carbide, silicon nitride, some other suitable dielectric(s), orany combination of the foregoing.

As used herein, a low κ dielectric is a dielectric with a dielectricconstant κ less than about 3.9, 3, 2, or 1. The lower wire 114 may be orcomprise, for example, aluminum copper, copper, aluminum, some suitableother suitable conductive material(s), or any combination of theforegoing.

The lower dielectric layer 104 separates the memory cell 102 from alower wire 114 underlying the memory cell 102 and the BEVA 106. Thelower dielectric layer 104 may be or comprise, for example, silicondioxide, silicon oxynitride, a low κ dielectric, silicon carbide,silicon nitride, some other suitable dielectric(s), or any combinationof the foregoing. As used herein, a low κ dielectric is a dielectricwith a dielectric constant κ less than about 3.9, 3, 2, or 1. The lowerwire 114 may be or comprise, for example, aluminum copper, copper,aluminum, some suitable other suitable conductive material(s), or anycombination of the foregoing.

The BEVA 106 extends from a bottom of the memory cell 102, through thelower dielectric layer 104, to the lower wire 114. In some embodiments,the BEVA 106 directly contacts the lower wire 114, and/or the topsurface 106 t of the BEVA 106 is even or substantially even with the topsurface 104 t of the lower dielectric layer 104. The top surface 106 tof the BEVA 106 is flat or substantially flat, such that an electricfield produced across the memory cell 102 using the BEVA 106 is uniformor substantially uniform. Further, the top surface of the BEVA 106 ishomogeneous (e.g., a single material). In some embodiments, the topsurface 106 t of the BEVA 106 extends continuously from a first sidewall106 s ₁ of the BEVA 106 to a second sidewall 106 s ₂ of the BEVA 106,where the first and second sidewalls 106 s ₁, 106 s ₂ are on oppositesides of the BEVA 106 and contact sidewalls of the lower dielectriclayer 104.

The BEVA 106 comprises a BEVA liner (e.g., conductive liner) 106 l, alower BEVA body (e.g., lower via body) 106 lb, and an upper BEVA body(e.q., upper via body) 106 ub. The lower BEVA body 106 lb and the upperBEVA body 106 ub collectively define a conductive body of the BEVA 106.The upper BEVA body 106 ub overlies the lower BEVA body 106 lb and theBEVA liner 106 l, and defines the top surface 106 t of the BEVA 106.Further, the lower BEVA body 106 lb and the upper BEVA body 106 ubcollectively define a BEVA body, such that the lower BEVA body 106 lband the upper BEVA body 106 ub may also be referred to as segments of aBEVA body. In some embodiments, the upper BEVA body 106 ub directlycontacts a top surface 106 t ₂ of the lower BEVA body 106 lb. The upperBEVA body 106 ub and the lower BEVA body 106 lb may each be or comprise,for example, aluminum, copper, aluminum copper, tungsten, some othersuitable conductive material(s), or any combination of the foregoing.

In some embodiments, the upper BEVA body 106 ub is the same material asthe lower BEVA body 106 lb, and/or is integrated with the lower BEVAbody 106 lb. In other embodiments, the upper BEVA body 106 ub is adifferent material than the lower BEVA body 106 lb. In some embodiments,the upper BEVA body 106 ub is completely homogeneous (e.g., a singlematerial) and/or the lower BEVA body 106 lb is completely homogeneous(e.g., a single material). In some embodiments, the upper BEVA body 106ub is the same material as the bottom electrode 108, and/or isintegrated with the bottom electrode 108. For example, the upper BEVAbody 106 ub and the bottom electrode 108 may be formed by the samedeposition. In other embodiments, the upper BEVA body 106 ub is adifferent material than the bottom electrode 108.

The BEVA liner 106 l cups an underside of the lower BEVA body 106 lb soas to line a bottom surface of the lower BEVA body 106 lb and sidewallsof the lower BEVA body 106 lb. The BEVA liner 106 l blocks material fromthe lower BEVA body 106 lb from diffusing or otherwise moving out of thelower BEVA body 106 lb, and may be or comprise, for example, titaniumnitride, titanium, tantalum nitride, tantalum, some other suitableconductive barrier material(s) for the lower BEVA body 106 lb, or anycombination of the foregoing. In some embodiments, BEVA liner 106 lprotrudes to a location above the top surface 106 t ₂ of the lower BEVAbody 106 lb. Further, in some embodiments, the BEVA liner 106 lpartially lines sidewalls of the upper BEVA body 106 ub.

An upper dielectric layer 116 covers the lower dielectric layer 104 andthe memory cell 102, and further accommodates an upper wire 118 and aTEVA 120. The upper dielectric layer 116 may be or comprise, forexample, silicon dioxide, a low κ dielectric, silicon carbide, siliconnitride, some suitable other dielectric(s), or any combination of theforegoing. The upper wire 118 may be or comprise, for example, aluminumcopper, copper, aluminum, some other suitable conductive material(s), orany combination of the foregoing.

The TEVA 120 is directly between the upper wire 118 and the memory cell102, and extends from the upper wire 118, through the upper dielectriclayer 116, to the memory cell 102. In some embodiments, the TEVA 120 ishomogenous (e.g., a single material). In other embodiments, the TEVA 120is heterogeneous and comprises a TEVA body 120 b and a TEVA liner 120 l.The TEVA body 120 b may be or comprise, for example, copper, aluminumcopper, aluminum, tungsten, some other suitable conductive material(s),or any combination of the foregoing. The TEVA liner 120 l blocksmaterial of the TEVA body 120 b from diffusing or otherwise moving outof the TEVA 120, and may be or comprise, for example, titanium nitride,tantalum, tantalum nitride, some other suitable conductive barriermaterial(s) for the TEVA body 120 b, or any combination of theforegoing. In some embodiments in which the TEVA 120 is heterogeneous, atop surface 120 t of the TEVA 120 is heterogeneous, and is rough oruneven.

With reference to FIG. 2, a cross-sectional view 200 of some moredetailed embodiments of the IC of FIG. 1 is provided. As illustrated,the lower wire 114 is within a lower interlayer dielectric (ILD) layer202. The lower ILD layer 202 may be or comprise, for example, silicondioxide, silicon oxynitride, a low κ dielectric, silicon nitride, someother suitable dielectric(s), or any combination of the foregoing. Insome embodiments, the lower wire 114 comprises a lower wire body 114 band a lower wire liner 114 l. The lower wire body 114 b may be orcomprise, for example, aluminum copper, copper, aluminum, some othersuitable metal, some other suitable conductive material(s), or anycombination of the foregoing. The lower wire liner 114 l cups anunderside of the lower wire body 114 b so as to line a bottom surface ofthe lower wire body 114 b and sidewalls of the lower wire body 114 b.Further, the lower wire liner 114 l blocks material from the lower wirebody 114 b from diffusing or otherwise moving out of the lower wire body114 b. The lower wire liner 114 l may be or comprise, for example,tantalum, titanium, titanium nitride, tantalum nitride, some othersuitable conductive barrier material(s) for the lower wire body 114 b,or any combination of the foregoing.

A BEVA dielectric layer 204 overlies the lower wire 114 and the lowerILD layer 202, and accommodates the BEVA 106. In some embodiments, theBEVA dielectric layer 204 comprise a lower BEVA dielectric layer 204 land an upper BEVA dielectric layer 204 u overlying the lower BEVAdielectric layer 204 l. Further, in some embodiments, the upper andlower BEVA dielectric layers 204 u, 204 l are different materials. Theupper and lower BEVA dielectric layers 204 u, 204 l may each be orcomprise, for example, silicon carbide, silicon nitride, some othersuitable dielectric(s), or any combination of the foregoing. In someembodiments, the upper BEVA dielectric layer 204 u is or comprisessilicon nitride, some other suitable nitride, or some other suitabledielectric, and/or the lower BEVA dielectric layer 204 l is siliconcarbide or some other suitable dielectric.

The BEVA 106 extends through the BEVA dielectric layer 204 from thelower wire 114 to the memory cell 102. In some embodiments, a width W ofthe BEVA 106 is uniform or substantially uniform from the lower wire 114to an interface between the upper and lower BEVA dielectric layers 204u, 204 l. Further, in some embodiments, the width W of the BEVA 106increases continuously from the interface to the top surface 106 t ofthe BEVA 106. The BEVA 106 comprises the BEVA liner 106 l, the lowerBEVA body 106 lb, and the upper BEVA body 106 ub. The upper BEVA body106 ub overlies the lower BEVA body 106 lb and defines the top surface106 t of the BEVA 106. The BEVA liner 106 l cups an underside of thelower BEVA body. The top surface 106 t of the BEVA 106 supports thememory cell 102 and is flat or substantially flat to promote a uniformor substantially uniform electric field across the memory cell 102.Further, the top surface 106 t of the BEVA 106 is also homogeneous.

The memory cell 102 reversibly changes between a first data state and asecond data state depending upon a voltage applied across the memorycell 102, and may be, for example, a RRAM cell, a MRAM cell, or someother suitable type of memory cell. In some embodiments where the memorycell 102 is an RRAM cell, the data storage element 110 of the memorycell 102 is normally insulating. However, the data storage element 110can be made to conduct through conductive filaments 110 f formed in thedata storage element 110 by application of an appropriate voltage acrossthe memory cell 102. For ease of illustration, only one of theconductive filaments 110 f is labeled 110 f. Once the conductivefilaments 110 f are formed, the conductive filaments 110 f may be reset(e.g., broken, resulting in a high resistance) or set (e.g., re-formed,resulting in a lower resistance) by application of an appropriatevoltage across the memory cell 102. The low and high resistances may beused to indicate a digital signal (i.e., “1” or “0”), thereby allowingfor data storage.

A hard mask 206 overlies the memory cell 102, and a spacer 208 overliesthe data storage element 110 of the memory cell 102. The spacer 208comprises a pair of segments respectively bordering opposite sidewallsof the top electrode 112 of the memory cell 102. In some embodiments,the segments respectively border opposite sidewalls of the hard mask 206that are respectively aligned with the opposite sidewalls of the topelectrode 112.

In some embodiments, the spacer 208 extends laterally along sidewalls ofthe top electrode 112 in a closed path to completely enclose the topelectrode 112. Note that this is not visible within the cross-sectionalview 200 of FIG. 2. In some embodiments, the spacer 208 is sunken into atop surface of the data storage element 110 (e.g., due to over etching).The hard mask 206 and the spacer 208 may each be or comprise, forexample, silicon nitride, silicon oxide, silicon oxynitride, some othersuitable dielectric(s), or any combination of the foregoing.

A capping layer 210 lines sidewalls of the memory cell 102 and sidewallsof the spacer 208, and further overlies the hard mask 206 and the BEVAdielectric layer 204. Further, a device ILD layer 212 overlies thecapping layer 210 and the BEVA dielectric layer 204. The capping layer210 may be or comprise, for example, silicon oxide, some other suitableoxide(s), some other dielectric(s), or any combination of the foregoing.The device ILD layer 212 may be or comprise, for example, silicondioxide, a low κ dielectric, silicon nitride, some other suitabledielectric(s), or any combination of the foregoing.

The upper wire 118 overlies the memory cell 102 and the device ILD layer212, within an upper ILD layer 214. The upper ILD layer 214 may be orcomprise, for example, silicon dioxide, a low κ dielectric, siliconnitride, some other suitable dielectric(s), or any combination of theforegoing. In some embodiments, the upper wire 118 comprises an upperwire body 118 b and an upper wire liner 118 l. The upper wire body 118 bmay be or comprise, for example, aluminum copper, copper, aluminum, someother suitable metal(s), some other suitable conductive material(s), orany combination of the foregoing. The upper wire liner 118 l cups anunderside of the upper wire body 118 b so as to line a bottom surface ofthe upper wire body 118 b and sidewalls of the upper wire body 118 b.Further, the upper wire liner 118 l blocks material from the upper wirebody 118 b from diffusing or otherwise moving out of the upper wire body118 b, and may be or comprise, for example, tantalum, titanium, titaniumnitride, tantalum nitride, some other suitable barrier material(s) forthe upper wire body 118 b, or any combination of the foregoing.

The TEVA 120 is in the device ILD layer 212 and extends from the upperwire 118, through the device ILD layer 212, to the memory cell 102. Insome embodiments, the TEVA 120 extends through the capping layer 210 andthe hard mask 206, and/or is sunken into a top of the top electrode 112of the memory cell 102. The TEVA 120 comprises a TEVA body 120 b and aTEVA liner 120 l The TEVA liner 120 l cups an underside of the TEVA body120 b and blocks material of the TEVA body 120 b from migrating out ofthe TEVA 120.

With reference to FIG. 3, an expanded cross-sectional view 300 of someembodiments of the IC of FIG. 2 is provided. The cross-sectional view200 of FIG. 2 may, for example, be taken within box BX. As illustrated,the IC includes a memory region 302 and a logic region 304. The memoryregion 302 accommodates the memory cell 102. The memory cell 102 restson the BEVA 106 and underlies the TEVA 120. The BEVA 106 has a topsurface that is homogeneous. Further, the top surface of the BEVA 106 isflat or substantially flat, so as to produce a uniform electric fieldacross the memory cell 102.

In some embodiments, the memory cell 102 is one of many memory cellsdefining a memory cell array (not labeled) in the memory region 302. Insome embodiments, each memory cell of the memory cell array is as thememory cell 102 is shown and described with respect to FIG. 1 and/orFIG. 2.

In some embodiments, each memory cell of the memory cell array rests ona BEVA and underlies a TEVA. Each TEVA of the memory cell array may, forexample, be as the TEVA 120 is shown and described with respect to FIG.1 and/or FIG. 2. Each BEVA of the memory cell array may, for example, beas the BEVA 106 is shown and described with respect to FIG. 1 and/orFIG. 2 so as to produce a uniform or substantially uniform electricfield across a corresponding memory cell. In some embodiments, eachmemory cell of the memory cell array overlies and is electricallycoupled to an access device 306. The access device 306 facilitatesaccess or selection of a corresponding memory cell in the memory cellarray and may be, for example, an insulated gate field-effect transistor(IGFET), a metal-oxide-semiconductor field-effect transistor (MOSFET),or some other suitable type of semiconductor device.

The logic region 304 accommodates a logic device 308. The logic device308 may be or comprise, for example, an IGFET, a MOFSET, or some othersuitable type of semiconductor device. In some embodiments, the logicdevice 308 is one of many logic devices defining a logic core (notlabeled). In some of such embodiments, operation of the logic core issupported or aided by the memory cell array, and/or the memory cellarray is embedded memory. Further, in some embodiments, the logic device308 supports operation of the memory cell 102 and/or the memory cellarray. For example, the logic device 308 may facilitate reading and/orwriting data of to the memory cell 102 and/or the memory cell array.

In addition to the memory cell 102 and the logic device 308, the ICfurther comprises a semiconductor substrate 310 and a BEOL interconnectstructure 312. The semiconductor substrate 310 supports and partiallydefines the logic device 308 and, in some embodiments, the access device306. In some embodiments, the semiconductor substrate 310 furthersupports and partially defines a logic core that includes the logicdevice 308. The semiconductor substrate 310 may be, for example, a bulksilicon substrate, a silicon-on-insulator (SOI) substrate, or some othersuitable type of semiconductor substrate. The BEOL interconnectstructure 312 overlies the semiconductor substrate 310 and accommodatesthe memory cell 102. In some embodiments, the BEOL interconnectstructure 312 further overlies and accommodates a memory cell array thatincludes the memory cell 102. The BEOL interconnect structure 312comprises a dielectric stack and a plurality of conductive features.

The dielectric stack comprises a lower ILD layer 202 covering thesemiconductor substrate 310 and the logic device 308. In someembodiments, the lower ILD layer 202 further covers the access device306. The dielectric stack further comprises a BEVA dielectric layer 204covering the lower ILD layer 202, a device ILD layer 212 covering theBEVA dielectric layer 204, and an upper ILD layer 214 covering thedevice ILD layer 212.

The conductive features are stacked in the dielectric stack to defineconductive paths interconnecting the memory cell 102, the logic device308, and other devices of the IC (e.g., the access device 306). Theconductive features include the lower wire 114, the upper wire 118, theBEVA 106, and the TEVA 120. Further, the conductive features include aplurality of additional vias 314 and a plurality of additional wires316. The additional vias 314 and the additional wires 316 may be orcomprise, for example, tungsten, copper, aluminum copper, aluminum, someother suitable conductive material(s), or any combination of theforegoing.

While the foregoing discussion of FIGS. 1-3 dealt with memory on theBEVA 106, it is to be appreciated that other types of electronic devicesmay be on the BEVA 106. For example, a metal-insulator-metal (MIM)capacitor, some other suitable type of MIM structure, or some othersuitable type of electronic device may be on the BEVA 106.

With reference to FIGS. 4-6, 7A-7C, 8-20, a series of cross-sectionalviews 400-600, 700A-700C, 800-2000 of some embodiments of a method forforming an IC comprising a memory cell on a flat BEVA top surface isprovided. The IC may be, for example, the IC of FIG. 2.

As illustrated by the cross-sectional view 400 of FIG. 4, a substrate402 is provided or formed. The substrate 402 comprises a lower ILD layer202 and a lower wire 114. Further, in some embodiments, the substrate402 comprises the semiconductor substrate 310 of FIG. 3, a portion ofthe interconnect structure 312 of FIG. 3 that is below the BEVAdielectric layer 204, the access device 306 of FIG. 3, the logic device308 of FIG. 3, or any combination of the foregoing. The lower ILD layer202 may be or comprise, for example, silicon nitride, silicon oxide, alow κ dielectric layer, some other suitable dielectric(s), or anycombination of the foregoing. The lower wire 114 is recessed into a topof the lower ILD layer 202, such that a top surface of the lower wire114 is even or substantially even with a top surface of the lower ILDlayer 202. The lower wire 114 may be or comprise, for example, titaniumnitride, tantalum, tantalum nitride, titanium, aluminum, aluminumcopper, copper, some other suitable conductive material(s), or anycombination of the foregoing. In some embodiments, the lower wire 114 isheterogeneous (e.g., multiple materials) and comprises a lower wire body114 b and a lower wire liner 114 l. The lower wire liner 114 l cups anunderside of the lower wire body 114 b and blocks material of the lowerwire body 114 b from migrating to surrounding structure. The lower wireliner 114 l may be or comprise, for example, titanium, tantalum,titanium nitride, tantalum nitride, some other suitable barriermaterial(s) for the lower wire body 114 b, or any combination of theforegoing. The lower wire body 114 b may be or comprise, for example,copper, aluminum copper, aluminum, some other suitable conductivematerial(s), or any combination of the foregoing.

Also illustrated by the cross-sectional view 400 of FIG. 4, a BEVAdielectric layer 204 is formed covering the substrate 402. The BEVAdielectric layer 204 may be or comprise, for example, silicon carbide,silicon nitride, silicon oxide, silicon oxynitride, some other suitabledielectric(s), or any combination of the foregoing. In some embodiments,the BEVA dielectric layer 204 comprises a lower BEVA dielectric layer204 l and an upper BEVA dielectric layer 204 u covering the lower BEVAdielectric layer 204 l. The lower BEVA dielectric layer 204 l may be orcomprise, for example, silicon carbide or some other suitabledielectric, and/or the upper BEVA dielectric layer 204 u may be orcomprise, for example, silicon nitride or some other suitabledielectric. In some embodiments, a process for forming the BEVAdielectric layer 204 comprises chemical vapor deposition (CVD), physicalvapor deposition (PVD), some other suitable deposition process(es), orany combination of the foregoing. As used herein, a term (e.g., process)with a suffix of “(es)” may, for example, be singular or plural.

As illustrated by the cross-sectional view 500 of FIG. 5, a first etchis performed into the BEVA dielectric layer 204 to form a BEVA opening502 overlying and exposing the lower wire 114. In some embodiments, uponcompletion of the first etch, the upper BEVA dielectric layer 204 u hasa pair of slanted sidewalls 204 s in the BEVA opening 502 andrespectively on opposite sides of the BEVA opening 502, whereas thelower BEVA dielectric layer 204 l has a pair of vertical orsubstantially vertical sidewalls 204 v in the BEVA opening 502 andrespectively on the opposite sides.

In some embodiments, a process for performing the first etch comprisesforming a photoresist mask 504 on the BEVA dielectric layer 204. Thephotoresist mask 504 may, for example, be formed by depositing aphotoresist layer on the BEVA dielectric layer 204 and patterning thephotoresist layer with a layout of the BEVA opening 502. The depositingmay, for example, be performed by spin coating or some other suitabledeposition process, and/or the patterning may, for example, be performedby photolithography or some other suitable patterning process. One ormore first etchants are applied to the upper BEVA dielectric layer 204 uuntil the lower BEVA dielectric layer 204 l is reached by the firstetchant(s) to partially form the BEVA opening 502. One or more secondetchants are applied to the lower BEVA dielectric layer 204 l, throughthe BEVA opening 502 as partially formed, until the lower wire 114 isreached by the second etchant(s) to finish forming the BEVA opening 502.The photoresist mask 504 is thereafter removed.

As illustrated by the cross-sectional view 600 of FIG. 6, a BEVA linerlayer 602 is formed covering the BEVA dielectric layer 204, and isfurther formed lining the BEVA opening 502 (see FIG. 5) so as topartially fill the BEVA opening 502. In some embodiments, the BEVA linerlayer 602 conformally lines the BEVA opening 502. The BEVA liner layer602 is conductive and, in some embodiments, is homogenous (e.g., asingle material). The BEVA liner layer 602 may, for example, be orcomprise titanium, titanium nitride, tantalum, tantalum nitride, someother suitable conductive material(s), or any combination of theforegoing. Further, the BEVA liner layer 602 may, for example, be formedby CVD, PVD, some other suitable deposition process(es), or anycombination of the foregoing.

Also illustrated by the cross-sectional view 600 of FIG. 6, a lower BEVAbody layer (e.g., lower via body layer) 604 is formed covering the BEVAdielectric layer 204, and further filling a remainder of the BEVAopening 502 (see FIG. 5), over the BEVA liner layer 602. The lower BEVAbody layer 604 is conductive and, in some embodiments, is homogeneous(e.g., a single material). Further, the lower BEVA body layer 604 is adifferent material than the BEVA liner layer 602 and, in someembodiments, has a different hardness value than the BEVA liner layer602. The lower BEVA body layer 604 may be or comprise, for example,copper, aluminum copper, aluminum, tungsten, some suitable othermetal(s), some other suitable conductive material(s), or any combinationof the foregoing. In some embodiments, the BEVA liner layer 602 is orotherwise comprises a barrier material for the lower BEVA body layer 604so as to prevent material of the lower BEVA body layer 604 frommigrating through the BEVA liner layer 602 to surrounding structure. Thelower BEVA body layer 604 may be formed by, for example, CVD, PVD,sputtering, electroless plating, electroplating, some other suitableplating or deposition process(es), or any combination of the foregoing.

As illustrated by the cross-sectional view 700A of FIG. 7A, a firstplanarization is performed into a top surface 604 t of the lower BEVAbody layer 604 to flatten or substantially flatten the top surface 604t, and to recess the top surface 604 t. Further, the first planarizationstops before reaching the BEVA liner layer 602, so the BEVA liner layer602 remains fully covered by the lower BEVA body layer 604 uponcompletion of the first planarization. The first planarization may, forexample, be performed by a chemical mechanical polish (CMP) or someother suitable planarization process.

Alternatively, as illustrated by the cross-sectional view 700B of FIG.7B, the first planarization stops on the BEVA liner layer 602, so theBEVA liner layer 602 is exposed upon completion of the firstplanarization. Further, in some embodiments, the top surface 604 t ofthe lower BEVA body layer 604 is vertically offset from a top surface602 t of the BEVA liner layer 602. The vertical offset may, for example,be due to different hardnesses between the lower BEVA body layer 604 andthe BEVA liner layer 602. Namely, the different hardnesses may, forexample, cause the lower BEVA body layer 604 and the BEVA liner layer602 to be removed at different rates during the first planarization,thereby causing the vertical offset.

Alternatively, as illustrated by the cross-sectional view 700C of FIG.7C, the first planarization stops on the BEVA dielectric layer 204, sothe BEVA dielectric layer 204 is exposed upon completion of the firstplanarization. Further, the first planarization additionally recessesthe top surface 602 t of the BEVA liner layer 602. As in FIG. 7B, insome embodiments, the top surface 604 t of the lower BEVA body layer 604is vertically offset from the top surface 602 t of the BEVA liner layer602 due to, for example, different hardnesses between the lower BEVAbody layer 604 and the BEVA liner layer 602.

As should be appreciated, FIGS. 7A-7C are alternative embodiments of thesame process step(s) (e.g., the first planarization). Therefore, in someembodiments, the method proceeds from FIG. 6 to FIG. 8 via any one ofthe FIGS. 7A-7C. For example, the method may proceed from FIG. 6 to FIG.8 via FIG. 7A. As another example, the method may proceed from FIG. 6 toFIG. 8 via FIG. 7B. As yet another example, the method may proceed fromFIG. 6 to FIG. 8 via FIG. 7C. In some embodiments, the differencebetween FIGS. 7A-7C is the amount of the semiconductor structure of FIG.6 that is removed by the first planarization. For example, a firstamount of the semiconductor structure of FIG. 6 may be removed at FIG.7A, a second amount of the semiconductor structure of FIG. 6 may beremoved at FIG. 7B, and a third amount of the semiconductor structure ofFIG. 6 may be removed at FIG. 7C, where the third amount is greater thanthe second amount, which is greater than the first amount. Inalternative embodiments, the method proceeds from the process step(s) ofFIG. 6 to the process step(s) of FIG. 8 without the process step(s) ofFIGS. 7A-7C. In other words, the first planarization of FIGS. 7A-7C maybe omitted in alternative embodiments.

As illustrated by the cross-sectional view 800 of FIG. 8, a second etchis performed into the lower BEVA body layer 604 (see FIG. 6, 7A, 7B, or7C) and the BEVA liner layer 602 (see FIG. 6, 7A, 7B, or 7C) to etchback the lower BEVA body layer 604 and the BEVA liner layer 602. Thesecond etch recesses the top surface 604 t of the lower BEVA body layer604 (see FIG. 6, 7A, 7B, or 7C) and the top surface 602 t of the BEVAliner layer 602 (see FIG. 6, 7A, 7B, or 7C) to locations spaced below atop surface 204 t of the BEVA dielectric layer 204, thereby partiallyclearing the BEVA opening 502 and forming a BEVA liner 106 l and a lowerBEVA body 106 lb. In some embodiments, the top surface 602 t of the BEVAliner layer 602 is above the top surface 604 t of the lower BEVA bodylayer 604. In some embodiments, the top surface 602 t of the BEVA linerlayer 602 is even with the top surface 604 t of the lower BEVA bodylayer 604. In some embodiments, the top surface 602 t of the BEVA linerlayer 602 is below the top surface 604 t of the lower BEVA body layer604. The BEVA liner 106 l is formed from the BEVA liner layer 602, andthe lower BEVA body 106 lb is formed from the lower BEVA body layer 604.In some embodiments, the second etch also recesses the top surface 204 tof the BEVA dielectric layer 204 (albeit, at a slower rate than thelower BEVA body layer 604 and the BEVA liner layer 602) to decreases athickness T of the BEVA dielectric layer 204.

The second etch is performed by an etchant that preferentially etchesthe lower BEVA body layer 604 and the BEVA liner layer 602, relative tothe BEVA dielectric layer 204, so the BEVA dielectric layer 204 isminimally etched. For example, the etchant may have a first etch ratefor the lower BEVA body layer 604, a second etch rate for the BEVA linerlayer 602, and a third etch rate for the BEVA dielectric layer 204,where the first and second etch rates are greater than the third etchrate. In some embodiments, the first and second etch rates are the same.In some embodiments, the first etch rate is greater than the second etchrate. In some embodiments, the first etch rate is less than the secondetch rate. In some embodiments, the first etch rate(s) are between about3-15 time greater than the second etch rate(s), between about 1-20 timesgreater than the second etch rate(s), between about 1-5 times greaterthan the second etch rate(s), between about 13-27 time greater than thesecond etch rate(s), or some other suitable relationship between thefirst and second etch rates. The second etch may, for example, be a wetetch or a dry etch. In some embodiments, the etchant of the second etchcomprises hydrogen peroxide, some other suitable chemical solution(s),or any combination of the foregoing. In other embodiments, the etchantof the second etch comprises ions or some other suitable dry etchant(s).

In some embodiments, the second etch proceeds from any one of the FIGS.7A-7C. For example, the second etch may proceed from FIG. 7A. As anotherexample, the second etch may proceed from FIG. 7B. As yet anotherexample, the second etch may proceed from FIG. 7C. In some embodiments,depending upon which one of FIGS. 7A-7C that FIG. 8 proceeds from, theetch time for the second etch is varied. Further, in some embodiments,the etch time for the second etch is inversely proportional to theamount of the semiconductor structure of FIG. 6 that is removed by thefirst planarization of FIGS. 7A-7C. For example, the second etch has afirst etch time when proceeding from FIG. 7A, a second etch time whenproceeding from FIG. 7B, and a third etch time when proceeding from FIG.7C, where the third etch time is less than the second etch time, whichis less than the first etch time.

As illustrated by the cross-sectional view 900 of FIG. 9, an upper BEVAbody layer (e.g., upper via body layer) 902 is formed covering the BEVAdielectric layer 204, and further filling a portion of the BEVA opening502 (see FIG. 8) cleared by the second etch. The upper BEVA body layer902 is conductive and is homogeneous (e.g., a single material). In someembodiments, the upper BEVA body layer 902 is the same material as thelower BEVA body 106 lb. In other embodiments, the upper BEVA body layer902 is a different material than the lower BEVA body 106 lb. Forexample, the upper BEVA body layer 902 may be the same material as theBEVA liner 106 l or some other suitable barrier material for lower BEVAbody 106 lb. The upper BEVA body layer 902 may be, for example, copper,aluminum copper, aluminum, tungsten, some suitable other metal(s), orsome other suitable conductive material(s). The upper BEVA body layer902 may be formed by, for example, CVD, PVD, sputtering, electrolessplating, electroplating, some other suitable plating or depositionprocess(es), or any combination of the foregoing.

As illustrated by the cross-sectional view 1000 of FIG. 10, a secondplanarization is performed into the upper BEVA body layer 902 (see FIG.9) until the BEVA dielectric layer 204 is reached to form an upper BEVAbody 106 ub from the upper BEVA body layer 902. The second planarizationmay, for example, be performed by a chemical mechanical polish (CMP) orsome other suitable planarization process. The upper BEVA body 106 ub isin the BEVA opening 502 (see FIG. 8), and overlies the lower BEVA body106 lb and the BEVA liner 106 l. Further, the upper BEVA body 106 ub,the lower BEVA body 106 lb, and the BEVA liner 106 l collectively definea BEVA 106 in the BEVA opening 502, and the upper BEVA body 106 ubindividually defines a top surface 106 t of the BEVA 106.

The top surface 106 t of the BEVA 106 is homogenous because the topsurface 106 t is formed from the upper BEVA body layer 902, and becausethe upper BEVA body layer 902 is homogeneous. Similarly, the top surface106 t of the BEVA 106 is flat or substantially flat because the topsurface 106 t is formed from the upper BEVA body layer 902, and becausethe upper BEVA body layer 902 is homogeneous. In particular, because theupper BEVA body layer 902 is homogenous, it has a substantially uniformhardness throughout and hence a substantially uniform removal rateduring the second planarization. Therefore, the second planarizationuniformly or substantially uniformly removes material of the upper BEVAbody layer 902 to form the top surface 106 t of the BEVA 106 flat orsubstantially flat. Because the top surface 106 t of the BEVA 106 isflat or substantially flat, the electric field across a memory cellsubsequently formed on the BEVA 106 is uniform or substantially uniform.

As illustrated by the cross-sectional view 1100 of FIG. 11, a bottomelectrode layer 1102, a data storage layer 1104, and a top electrodelayer 1106 are formed on the BEVA 106 and the BEVA dielectric layer 204.The bottom electrode layer 1102 is formed covering the BEVA dielectriclayer 204 and the BEVA 106. The data storage layer 1104 is formedcovering the bottom electrode layer 1102. The top electrode layer 1106is formed covering the data storage layer 1104. The bottom and topelectrode layers 1102, 1106 are conductive, and may be or comprise, forexample, metals, metal nitrides, or some suitable other conductivematerial(s). The data storage layer 1104 reversibly changes between afirst data state (e.g., a first resistance) and a second data state(e.g., a second resistance) depending upon a voltage applied across thedata storage layer 1104. In some embodiments where the memory cell undermanufacture is an RRAM cell, the data storage layer 1104 may be orcomprise, for example, hafnium oxide, some other suitable high κdielectric(s), or some other suitable dielectric(s). In some embodimentswhere the memory cell under manufacture is an MRAM cell, the datastorage layer 1104 may be or comprise, for example, a MTJ layer or someother suitable magnetic storage structure. The MTJ layer may, forexample, comprise a first ferromagnetic layer, an insulating layeroverlying the first ferromagnetic layer, and a second ferromagneticlayer overlying the insulating layer. In some embodiments, the bottomand top electrode layers 1102, 1106 and the data storage layer 1104 areformed by CVD, PVD, electroless plating, electroplating, sputtering,some suitable other plating or deposition process(es), or anycombination of the foregoing.

As illustrated by the cross-sectional view 1200 of FIG. 12, a hard mask206 is formed covering a memory cell region of the top electrode layer1106 (see FIG. 11) that overlies the BEVA 106. The hard mask 206 may beor comprise, for example, silicon nitride, some other suitablenitride(s), some other suitable dielectric(s), or any combination of theforegoing. Further, the hard mask 206 may, for example, be formed bydepositing a hard mask layer on the top electrode layer 1106 andpatterning the hard mask layer into the hard mask 206. The depositingmay, for example, be performed by CVD, PVD, or some other suitabledeposition process, and/or the patterning may, for example, be performedby using a photolithography/etching process or some other suitablepatterning process.

Also illustrated by the cross-sectional view 1200 of FIG. 12, a thirdetch is performed into the top electrode layer 1106 (see FIG. 11) withthe hard mask 206 in place to form a top electrode 112 underlying thehard mask 206. In some embodiments, the data storage layer 1104 servesas an etch stop for the third etch and/or the third etch over extendsinto the data storage layer 1104 to partially etch the data storagelayer 1104.

As illustrated by the cross-sectional view 1300 of FIG. 13, a spacerlayer 1302 is formed covering and lining the structure of FIG. 12. Insome embodiments, the spacer layer 1302 is formed conformally, and/or isformed by CVD, PVD, some other suitable deposition process(es), or anycombination of the foregoing. The spacer layer 1302 may be, for example,silicon nitride, some other suitable nitride(s), some other suitabledielectric(s), or any combination of the foregoing.

As illustrated by the cross-sectional view 1400 of FIG. 14, a fourthetch is performed into the spacer layer 1302 (see FIG. 13) to etch backthe spacer layer 1302 and to form a spacer 208 from the spacer layer1302. The spacer 208 comprises a pair of segments respectively onopposite sidewalls of the top electrode 112. Further, in someembodiments, the segments are respectively on opposite sidewalls of thehard mask 206, and/or the opposite sidewalls of the hard mask 206 arerespectively even with the opposite sidewalls of the top electrode 112.In some embodiments, the spacer 208 extends laterally along sidewalls ofthe top electrode 112 in a closed path to completely enclose the topelectrode 112. Note that this is not visible within the cross-sectionalview 1400 of FIG. 14. A process for performing the fourth etch maycomprise, for example, applying one or more etchants to the spacer layer1302 to remove horizontal segments of the spacer layer 1302 withoutremoving vertical segments of the spacer layer 1302, such that at leastone of the vertical segments corresponds to the spacer 208.

As illustrated by the cross-sectional view 1500 of FIG. 15, a fifth etchis performed into the data storage layer 1104 (see FIG. 14) and thebottom electrode layer 1102 (see FIG. 14) with the spacer 208 and thehard mask 206 in place to form a data storage element 110 and a bottomelectrode 108. The data storage element 110 underlies the top electrode112 and is formed from the data storage layer 1104. The bottom electrode108 underlies the data storage element 110 and is formed from the bottomelectrode layer 1102. A process for performing the fifth etch maycomprise, for example, applying one or more etchants to the data storagelayer 1104 and the bottom electrode layer 1102 until the BEVA dielectriclayer 204 is reached by the etchant(s). The spacer 208 and the hard mask206 collectively define a mask for the fifth etch, and the BEVAdielectric layer 204 serves as an etch stop.

As illustrated by the cross-sectional view 1600 of FIG. 16, a cappinglayer 210 is formed covering the BEVA dielectric layer 204, the spacer208, and the hard mask 206. Further, the capping layer 210 is formedlining sidewalls of the spacer 208, sidewalls of the data storageelement 110, and sidewalls of the bottom electrode 108. The cappinglayer 210 may be or comprise, for example, silicon nitride, some othersuitable nitride(s), some other suitable dielectric(s), or anycombination of the foregoing. In some embodiments, the capping layer 210is formed by conformal deposition, and/or is formed by CVD, PVD, someother suitable deposition process(es), or any combination of theforegoing.

Also illustrated by the cross-sectional view 1600 of FIG. 16, a deviceILD layer 212 is formed covering the capping layer 210. Further, thedevice ILD layer 212 is formed with a top surface that is planar orsubstantially planar. The device ILD layer 212 may be or comprise, forexample, silicon oxide, a low κ dielectric, some other suitabledielectric(s), or any combination of the foregoing. In some embodiments,a process for forming the device ILD layer 212 comprises depositing thedevice ILD layer 212 covering the capping layer 210, and subsequentlyperforming a planarization into the top surface of the device ILD layer212. The device ILD layer 212 may, for example, be deposited by CVD,PVD, sputtering, some other suitable deposition process(es), or anycombination of the foregoing. The planarization may, for example, beperformed by a CMP or some other suitable planarization process.

As illustrated by the cross-sectional view 1700 of FIG. 17, a sixth etchis performed into the device ILD layer 212, the capping layer 210, andthe hard mask 206 to form a TEVA opening 1702 overlying and exposing thetop electrode 112. In some embodiments, a process for performing thesixth etch comprises forming a photoresist mask 1704 on the device ILDlayer 212. The photoresist mask 1704 may, for example, be formed bydepositing a photoresist layer on the device ILD layer 212 andpatterning the photoresist layer with a layout of the TEVA opening 1702.The depositing may, for example, be performed by spin coating or someother suitable deposition process, and/or the patterning may, forexample, be performed by photolithography or some other suitablepatterning process. One or more etchants are then be applied to thedevice ILD layer 212, the capping layer 210, and the hard mask 206 withthe photoresist mask 1704 in place, and the photoresist mask 1704 isthereafter removed.

As illustrated by the cross-sectional view 1800 of FIG. 18, a TEVA layer1802 is formed covering the device ILD layer 212 and filling the TEVAopening 1702 (see FIG. 17). The TEVA layer 1802 comprises a TEVA linerlayer 1802 l and a TEVA body layer 1802 b. The TEVA liner layer 1802 lcovers the device ILD layer 212 and lines the TEVA opening 1702 so as topartially fill the TEVA opening 1702. In some embodiments, TEVA linerlayer 1802 l conformally lines the TEVA opening 1702. The TEVA bodylayer 1802 b covers the TEVA liner layer 1802 l and fills a remainder ofthe TEVA opening 1702 over the TEVA liner layer 1802 l. The TEVA linerlayer 1802 l is a different material than the TEVA body layer 1802 b andhas a different hardness than the TEVA body layer 1802 b. Further, theTEVA liner layer 1802 l blocks material of the TEVA body layer 1802 bfrom migrating to surrounding structure. The TEVA body layer 1802 b maybe or comprise, for example, tungsten, copper, aluminum copper,aluminum, some suitable other metal, or some other suitable conductivematerial. The TEVA liner layer 1802 l may be or comprise, for example,titanium, tantalum, titanium nitride, tantalum nitride, or some othersuitable barrier material for the TEVA body layer 1802 b. The TEVA linerlayer 1802 l and the TEVA body layer 1802 b may, for example, be formedby CVD, PVD, electroless plating, electroplating, some other suitableplating or deposition process(es), or any combination of the foregoing.

As illustrated by the cross-sectional view 1900 of FIG. 19, a thirdplanarization is performed into a top of TEVA layer 1802 (see FIG. 18),including a top of the TEVA liner layer 1802 l (see FIG. 18) and a topof the TEVA body layer 1802 b (see FIG. 18), until the device ILD layer212 is reached to form a TEVA 120 in the TEVA opening 1702 (see FIG.17). The TEVA 120 comprises a TEVA body 120 b and a TEVA liner 120 l.The TEVA body 120 b is formed from the TEVA body layer 1802 b, and theTEVA liner 120 l is formed from the TEVA liner layer 1802 l. Further,the TEVA liner 120 l cups an underside of the TEVA body 120 b so as toline a bottom surface of the TEVA body 120 b and sidewalls of the TEVAbody 120 b. The third planarization may, for example, be performed by aCMP or some other suitable planarization process.

Because the TEVA 120 is formed from both the TEVA liner layer 1802 l andthe TEVA body layer 1802 b, and because the TEVA liner layer 1802 l andthe TEVA body layer 1802 b are different materials, the TEVA 120 isheterogeneous (e.g., multiple materials) and has a top surface 120 tthat is heterogeneous. Further, because the TEVA liner layer 1802 l andthe TEVA body layer 1802 b are different materials, the TEVA liner layer1802 l and the TEVA body layer 1802 b have different hardnesses and,hence, different removal rates during the third planarization.Accordingly, the third planarization non-uniformly removes material fromthe TEVA liner layer 1802 l and the TEVA body layer 1802 b. This, inturn, forms the TEVA 120 so the top surface 120 t of the TEVA 120 thatis rough or uneven.

As illustrated by the cross-sectional view 2000 of FIG. 20, an upper ILDlayer 214 and an upper wire 118 are formed on the device ILD layer 212and the TEVA 120. The upper ILD layer 214 may be or comprise, forexample, silicon nitride, silicon oxide, a low κ dielectric layer, someother suitable dielectric(s), or any combination of the foregoing. Theupper wire 118 is recessed into a bottom of the upper ILD layer 214,such that a bottom surface of the upper wire 118 is even orsubstantially even with a bottom surface of the upper ILD layer 214.Further, the upper wire 118 overlies and is electrically coupled to theTEVA 120. The upper wire 118 may be or comprise, for example, titaniumnitride, tantalum, tantalum nitride, titanium, aluminum, aluminumcopper, copper, some other suitable conductive material(s), or anycombination of the foregoing. In some embodiments, the upper wire 118 isheterogeneous (e.g., multiple materials) and comprises an upper wirebody 118 b and an upper wire liner 118 l. The upper wire body 118 b maybe or comprise, for example, copper, aluminum copper, aluminum, or someother suitable conductive material. The upper wire liner 118 l cups anunderside of the upper wire body 118 b and blocks material of the upperwire body 118 b from migrating to surrounding structure. The upper wireliner 118 l may be, for example, titanium, tantalum, titanium nitride,tantalum nitride, or some other suitable barrier material for the upperwire body 118 b.

In some embodiments where the data storage element 110 corresponds toRRAM, a forming voltage is applied across the data storage element 110,from the bottom electrode 108 to the top electrode 112, to form one ormore conductive filaments (not shown) in the data storage element 110.Examples of the conductive filament(s) are shown in FIG. 2 (see theconductive filaments 110 f in FIG. 2).

With reference to FIG. 21, a flowchart 2100 of some embodiments ofmethod of FIGS. 4-6, 7A-7C, 8-20 is provided.

At 2102, a BEVA dielectric layer is formed covering a substrate. See,for example, FIG. 4. The substrate comprises a lower ILD layer and alower wire. The lower wire is recessed into a top of a lower ILD layer,such that a top surface of the lower wire is even or substantially evenwith a top surface of the lower ILD layer. The lower ILD layer and thelower wire may, for example, be components of a BEOL interconnectstructure.

At 2104, a first etch is performed into the BEVA dielectric layer toform a BEVA opening overlying and exposing the lower wire. See, forexample, FIG. 5.

At 2106, a BEVA liner layer and a lower BEVA body layer are formedcovering the BEVA dielectric layer and filling the BEVA opening. See,for example, FIG. 6. The BEVA liner layer lines the BEVA opening topartially fill the BEVA opening, and the lower BEVA body layer fills aremainder of the BEVA opening over the BEVA liner layer. The lower BEVAbody layer is conductive and, in some embodiments, homogeneous. The BEVAliner is conductive and blocks material of the lower BEVA body layerfrom migrating (e.g., diffusing) out of the BEVA opening.

At 2108, a top surface of the BEVA liner layer and a top surface of thelower BEVA body layer are recessed to form a BEVA liner and a lower BEVAbody in the BEVA opening, and to partially clear the BEVA opening. See,for example, FIGS. 7A-7C and 8. The recessing may, for example, beperformed by a planarization followed by an etch back.

At 2110, an upper BEVA body layer is formed covering the BEVA dielectriclayer and filling a cleared portion of the BEVA opening. See, forexample, FIG. 9. The upper BEVA body layer is homogeneous.

At 2112, a planarization is performed into the upper BEVA body layeruntil the BEVA dielectric layer is reached to form an upper BEVA body inthe BEVA opening. See, for example, FIG. 10. The BEVA liner, the upperBEVA body, and the lower BEVA body define a BEVA with a top surface thatis homogenous, and that is flat or substantially flat. The top surfaceof the BEVA is flat or substantially flat because the top surface isformed from the upper BEVA body layer. Namely, because the upper BEVAbody layer is homogeneous, the upper BEVA body layer is removed at auniform or substantially uniform rate during the planarization, therebyforming the top surface of the BEVA flat or substantially flat. Becausethe top surface of the BEVA is flat or substantially flat, an electricfield produced using the BEVA is uniform or substantially uniform.

At 2114, a memory cell is formed on the BEVA. See, for example, FIGS.11-15. The memory cell may be, for example, an RRAM cell, a MRAM cell,or some other suitable type of memory cell. In other embodiments,another type of electronic device is formed on the BEVA, such as, forexample, a metal-insulator-metal (MIM) capacitor or some other suitabletype of electronic device.

At 2116, a device ILD layer is formed covering the memory cell and theBEVA dielectric layer. See, for example, FIG. 16.

At 2118, a TEVA is formed extending through the device ILD layer to atop electrode of the memory cell. See, for example, FIGS. 17-19.

At 2120, an upper ILD layer and an upper wire are formed on the deviceILD layer and the TEVA. See, for example, FIG. 20. The upper wireoverlies the TEVA and is recessed into a bottom of the upper ILD layer,such that a bottom surface of the upper wire is even or substantiallyeven with a bottom surface of the upper ILD layer. The upper ILD layerand the upper wire may, for example, be components of a BEOLinterconnect structure.

While the flowchart 2100 of FIG. 21 is illustrated and described hereinas a series of acts or events, it will be appreciated that theillustrated ordering of such acts or events is not to be interpreted ina limiting sense. For example, some acts may occur in different ordersand/or concurrently with other acts or events apart from thoseillustrated and/or described herein. Further, not all illustrated actsmay be required to implement one or more aspects or embodiments of thedescription herein, and one or more of the acts depicted herein may becarried out in one or more separate acts and/or phases.

Therefore, in some embodiments, the present application is directedtowards an integrated circuit including: a conductive wire; a viadielectric layer overlying the conductive wire; a via extending throughthe via dielectric layer to the conductive wire, wherein the viaincludes a conductive body and a conductive liner, wherein theconductive liner cups an underside of the conductive body and has a topsurface recessed below a top surface of the via, and wherein theconductive body overhangs the top surface of the conductive liner anddefines the top surface of the via; and a memory cell directly on thetop surface of the via. In some embodiments, the top surface of the viaextends continuously from a first sidewall of the via to a secondsidewall of the via, wherein the first and second sidewalls of the viaare on opposite sides of the via and directly contact the via dielectriclayer. In some embodiments, the memory cell includes a bottom electrode,a data storage element overlying the bottom electrode, and a topelectrode overlying the data storage element, wherein a bottom surfaceof the bottom electrode directly contacts the top surface of the via anda top surface of the via dielectric layer. In some embodiments, theconductive liner is continuous and directly contacts sidewalls of thevia dielectric layer and sidewalls of the conductive body, wherein theconductive liner has an upper surface recessed below the top surface ofthe conductive liner, and wherein the conductive body directly contactsthe top surface of the conductive liner and the upper surface of theconductive liner. In some embodiments, the conductive liner directlycontacts the conductive wire. In some embodiments, the conductive linerblocks diffusion of material from the conductive body to the viadielectric layer and the conductive wire. In some embodiments, the viadielectric layer includes a lower dielectric layer and an upperdielectric layer overlying and directly contacting the lower dielectriclayer, wherein a width of the via continuously decreases from the topsurface of the via to an interface between the lower and upperdielectric layers, and wherein the width of the via is substantiallyuniform from the interface to the conductive wire. In some embodiments,the top surface of the via is homogeneous. In some embodiments, theconductive body includes copper, wherein the conductive liner includestitanium nitride, titanium, tantalum nitride, or tantalum.

In other embodiments, the present application is directed towards amethod for forming an integrated circuit, the method including:performing an etch into a via dielectric layer to form an openingoverlying and exposing a conductive wire underlying the via dielectriclayer; forming a via liner layer covering the via dielectric layer andlining the opening, wherein the via liner layer partially fills theopening; forming a lower via body layer covering the via dielectriclayer and filling a remainder of the opening over the via liner layer;recessing a top surface of the lower via body layer and a top surface ofthe via liner layer to below a top surface of the via dielectric layerto partially clear the opening, and to form a via liner and a lower viabody in the opening; forming an upper via body layer covering the viadielectric layer, and filling a portion of the opening cleared by therecessing; and performing a planarization into the upper via body layeruntil the via dielectric layer is reached to form an upper via body inthe opening. In some embodiments, the lower via body, the upper viabody, and the via liner collectively define a via in the opening,wherein the upper via body completely defines a top surface of the via.In some embodiments, the upper via body layer is a single material. Insome embodiments, the recessing includes: performing a secondplanarization into the top surface of the lower via body layer; andperforming a second etch into the top surface of the lower via bodylayer and the top surface of the via liner layer to form the via linerand the lower via body. In some embodiments, the second planarizationstops before reaching the via liner layer and the via dielectric layer,such that the via liner layer is covered by the lower via body layeroutside the opening upon completion of the second planarization. In someembodiments, the second planarization stops on the via liner layer,before reaching the via dielectric layer, such that the via liner layeris uncovered by the lower via body layer outside the opening uponcompletion of the second planarization. In some embodiments, the secondplanarization stops on the via dielectric layer, wherein the top surfaceof the via liner layer is vertically offset from the top surface of thelower via body layer upon completion of the second planarization. Insome embodiments, the second etch is performed using an etchant thatetches the lower via body layer and the via liner layer at a faster ratethan the via dielectric layer. In some embodiments, the via liner layerdirectly contacts sidewalls of the via dielectric layer in the opening,wherein the lower via body layer directly contacts the via liner layerand is spaced from the via dielectric layer by the via liner layer. Insome embodiments, the upper via body layer directly contacts sidewallsof the via dielectric layer, sidewalls of the via liner, a top surfaceof the via liner, and a top surface of the lower via body in theopening.

In other embodiments, the present application is directed towardsanother integrated circuit including: a conductive wire; a viadielectric layer overlying the conductive wire; a via extending throughthe via dielectric layer to the conductive wire, wherein the viaincludes a conductive body and a conductive liner, wherein theconductive body includes a pair of first sidewalls and a pair of secondsidewalls, wherein the first sidewalls are above the second sidewallsand are respectively on opposite sides of the via, wherein the secondsidewalls are respectively on the opposite sides of the via, wherein thesecond sidewalls are laterally between and laterally spaced from thefirst sidewalls, and wherein the conductive liner extends continuouslyfrom a bottom edge of one of the first sidewalls, along the secondsidewalls, to a bottom edge of another one of the first sidewalls; and amemory cell directly on the via.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit (IC) comprising: aconductive wire; a via dielectric layer overlying the conductive wire; avia extending through the via dielectric layer to the conductive wire,wherein the via comprises a conductive body and a conductive liner,wherein the conductive liner cups an underside of the conductive bodyand has a top surface that is recessed below a top surface of the viaand that is elevated above a bottom surface of the conductive body, andwherein the conductive body overhangs the top surface of the conductiveliner and defines the top surface of the via; and a memory cell directlyon the top surface of the via.
 2. The IC according to claim 1, whereinthe top surface of the via extends continuously from a first sidewall ofthe via to a second sidewall of the via, and wherein the first andsecond sidewalls of the via are on opposite sides of the via anddirectly contact the via dielectric layer.
 3. The IC according to claim1, wherein the memory cell comprises a bottom electrode, a data storageelement overlying the bottom electrode, and a top electrode overlyingthe data storage element, and wherein a bottom surface of the bottomelectrode directly contacts the top surface of the via and a top surfaceof the via dielectric layer.
 4. The IC according to claim 1, wherein theconductive liner is continuous and directly contacts sidewalls of thevia dielectric layer and sidewalls of the conductive body, wherein theconductive liner has an upper surface recessed below the top surface ofthe conductive liner, and wherein the conductive body directly contactsthe top surface of the conductive liner and the upper surface of theconductive liner.
 5. The IC according to claim 1, wherein the conductiveliner blocks diffusion of material from the conductive body to the viadielectric layer and the conductive wire.
 6. The IC according to claim1, wherein the via dielectric layer comprises a lower dielectric layerand an upper dielectric layer overlying and directly contacting thelower dielectric layer, wherein a width of the via continuouslydecreases from the top surface of the via to an interface between thelower and upper dielectric layers, and wherein the width of the via issubstantially uniform from the interface to the conductive wire.
 7. TheIC according to claim 1, wherein the top surface of the via ishomogeneous.
 8. The IC according to claim 1, wherein the conductive bodycomprises copper, and wherein the conductive liner comprises titaniumnitride, titanium, tantalum nitride, or tantalum.
 9. The IC according toclaim 1, wherein the conductive liner has a U-shaped profile that wrapsaround a downward protrusion of the conductive body.
 10. An integratedcircuit comprising: a conductive wire; a via dielectric layer overlyingthe conductive wire; a via extending through the via dielectric layer tothe conductive wire, wherein the via comprises a conductive body and aconductive liner, wherein the conductive body comprises a pair of firstsidewalls and a pair of second sidewalls, wherein the first sidewallsare above the second sidewalls and are respectively on opposite sides ofthe via, wherein the second sidewalls are respectively on the oppositesides of the via, wherein the second sidewalls are laterally between andlaterally spaced from the first sidewalls, and wherein the conductiveliner extends continuously from a bottom edge of one of the firstsidewalls, along the second sidewalls, to a bottom edge of another oneof the first sidewalls; and a memory cell directly on the via.
 11. Theintegrated circuit according to claim 10, wherein the conductive linerdirectly contacts sidewalls of the via dielectric layer and a topsurface of the conductive wire, wherein the conductive body directlycontacts sidewalls of the conductive liner, the sidewalls of the viadielectric layer, a top surface of the conductive liner, and an uppersurface of the conductive liner recessed below the top surface of theconductive liner.
 12. The integrated circuit according to claim 10,wherein the via dielectric layer comprises a lower via dielectric layerand an upper via dielectric layer overlying and directly contacting thelower via dielectric layer, wherein top edges of the first sidewalls areat a top surface of the via, wherein bottom edges of the first sidewallsand top edges of the second sidewalls are vertically above aninter-dielectric interface between the lower and upper via dielectriclayers, and wherein bottom edges of the second sidewalls are at an uppersurface of the conductive liner.
 13. The integrated circuit according toclaim 10, wherein the first sidewalls of the conductive body slantlaterally in opposite directions.
 14. The integrated circuit accordingto claim 10, wherein the second sidewalls each comprise a verticalsegment and a slanted segment overlying the vertical segment.
 15. Theintegrated circuit according to claim 14, wherein the via dielectriclayer comprises a lower via dielectric layer and an upper via dielectriclayer overlying and directly contacting the lower via dielectric layerat an inter-dielectric interface, and wherein the slanted segment meetsthe vertical segment at a location about even with the inter-dielectricinterface.
 16. The integrated circuit according to claim 10, wherein thesecond sidewalls are laterally space from the first sidewalls by adistance about equal to a thickness of the conductive liner.
 17. Anintegrated circuit comprising: a lower wire; a via dielectric layeroverlying the lower wire; a first via extending through the viadielectric layer to directly contact the lower wire, wherein the firstvia comprises a conductive body and a conductive liner, wherein theconductive liner has a pair of top corners, wherein the top corners arerespectively on opposite sides of the first via, and wherein theconductive body wraps around the top corners from sidewalls of theconductive liner to a top surface of the conductive liner; a memory celldirectly on a top surface of the conductive body; a second via overlyingand directly contacting the memory cell; and an upper wire overlying anddirectly contacting the second via.
 18. The integrated circuit accordingto claim 17, wherein the second via has a top surface that comprisesdifferent materials respectively at edges of the top surface and acenter of the top surface, and wherein the top surface of the conductivebody completely defines a top surface of the first via and is a singlematerial.
 19. The integrated circuit according to claim 17, wherein thesecond via comprises a second conductive body and a second conductiveliner, wherein the second conductive body and the second conductiveliner are different conductive materials, and wherein the secondconductive liner cups an underside of the second conductive body and hasa top surface vertically offset from a top surface of the secondconductive body.
 20. The integrated circuit according to claim 17,further comprising a substrate, wherein the substrate comprises: asemiconductor substrate comprising a logic region and a memory region; alogic device recessed in a top of the semiconductor substrate and withinthe logic region of the semiconductor substrate; an access devicerecessed in the top of the semiconductor substrate and within the memoryregion of the semiconductor substrate; and an interconnect structurecovering the semiconductor substrate, the logic device, and the accessdevice, wherein the interconnect structure comprises the lower wire, andwherein the lower wire is recessed into a top of the interconnectstructure and is electrically coupled to the access device.